The invention relates to a measuring resistor, in particular a low-resistance current sense resistor. The invention also relates to a corresponding measuring method.
It has been known for some years from the prior art (e.g. DE 42 43 349 A1) to use low-resistance current sense resistors (“shunts”) to measure current by what is known as the four-wire technique. In this technique, the electric current to be measured is fed into the low-resistance current sense resistor, and the voltage drop across the resistor element of the low-resistance current sense resistor is measured. According to Ohm's law, the measured voltage is then a measure of the electric current flowing through the current sense resistor.
Such current sense resistors can have a planar design, such as is described in EP 0 605 800 A1 and DE 42 43 349 A1 for example. WO 2007/068409 A1 and DE 10 2005 059 561 A1, for example, describe a different design for such current sense resistors in the form of a coaxial resistor.
The measurement precision of these known current sense resistors, however, is not yet completely satisfactory.
Reference is also made to the prior art document U.S. Pat. No. 6,181,234 B1. This document discloses a planar low-value resistor having a centrally arranged resistive strip, which can be made of a nickel-aluminum alloy for instance. Two thermally conductive elements, which are likewise planar and may be made of copper, for example, and are used solely for buffering and dissipating generated heat, are welded to the two opposite side edges of the resistive strip. In this arrangement, five contact pairs are formed side by side on the top face of the thermally conductive element. One of these contact pairs is used here to measure the voltage drop across the resistive strip, whereas the other contact pairs are used for conducting in and out the electric current, which facilitates a current measurement by means of the known four-wire technique. In this case, the voltage drop across the resistor is again measured at one specific position by means of a single contact pair. It should also be mentioned in this connection that the planar thermally conductive elements at the sides of the resistive strip are not themselves used for making the electrical contact, and also are not suitable for this purpose. This known resistor thus has a fundamentally different design and is therefore not of the type in question.
Finally, reference is made to DE 10 2006 039 722 A1 and to DE 10 2012 211 749 A1 as prior art documents. These documents, however, disclose different types of resistors and are therefore likewise not of the type in question.
Therefore the object of the invention is to make appropriate improvements to the known measuring resistors.
This object is achieved by a measuring resistor and a corresponding measuring method according to the invention.